Flowable film dielectric gap fill process

ABSTRACT

Methods of this invention relate to filling gaps on substrates with a solid dielectric material by forming a flowable film in the gap. The flowable film provides consistent, void-free gap fill. The film is then converted to a solid dielectric material. In this manner gaps on the substrate are filled with a solid dielectric material. According to various embodiments, the methods involve reacting a dielectric precursor with an oxidant to form the dielectric material. In certain embodiments, the dielectric precursor condenses and subsequently reacts with the oxidant to form dielectric material. In certain embodiments, vapor phase reactants react to form a condensed flowable film.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority from U.S.patent application Ser. No. 12/984,524, to be issued as U.S. Pat. No.8,481,403 on Jul. 9, 2013, filed Jan. 4, 2011, titled “FLOWABLE FILMDIELECTRIC GAP FILL PROCESS,” which is a continuation of U.S.application Ser. No. 12/411,243, now U.S. Pat. No. 7,888,233, filed Mar.25, 2009, titled “FLOWABLE FILM DIELECTRIC GAP FILL PROCESS,” which is acontinuation of U.S. patent application Ser. No. 11/447,594, now U.S.Pat. No. 7,524,735, filed Jun. 5, 2006, titled “FLOWABLE FILM DIELECTRICGAP FILL PROCESS,” which is a continuation-in-part of U.S. patentapplication Ser. No. 10/810,066, now U.S. Pat. No. 7,074,690, filed Mar.25, 2004, titled “SELECTIVE GAP-FILL PROCESS,” and which is also acontinuation-in-part of U.S. patent application Ser. No. 11/323,812, nowU.S. Pat. No. 7,582,555, filed Dec. 29, 2005, titled “CVD FLOWABLE GAPFILL.” All of these applications are hereby incorporated in theirentireties by this reference.

FIELD OF THE INVENTION

This invention relates to methods for dielectric gap-fill. Morespecifically, the methods involve provide bottom-up fill of dielectricsby forming a flowable film in the gaps on a substrate.

BACKGROUND

Many deposition processes have difficulty filling the small trenches andother gap features used in current semiconductor processing schemes.Individual trenches and other gap type features produced in any giventechnology node have principal dimensions that are significantly smallerthan the critical dimensions that define the current technology. Thus,it is not unusual to find gaps on the order of 100 nm or less. In futureyears, these feature sizes will shrink to even smaller dimensions.Unless the processes are extremely conformal, the gaps pinch off attheir necks. Compounding the problem is the fact that many of these gapshave relatively high aspect ratios, on the order of at least 6:1.Examples of situations where one can find these dimensions andgeometries include damascene copper line processes, shallow trenchisolation, and interlayer dielectric (ILD) applications.

Filling such trenches in a reliable manner, while avoiding voids in thefill material is particularly challenging at this scale. Currentprocesses including Physical Vapor Deposition (PVD) and Plasma EnhancedChemical Vapor Deposition (PECVD), including High Density PlasmaChemical Vapor Deposition (HDP CVD), each of which presents some issuesfor filling small dimension, high aspect ratio features. Conformaldeposition techniques may be inappropriate for situations where thedimension of the neck is narrower than the rest of the feature. This isbecause the conformal nature of the deposition leads to “pinching off”,where the reentrant features are not completely filled before theentrance to the feature is sealed off. In addition, conformal depositionoften leads to weak spots or seams in structures with vertical walls.

What is therefore needed is an improved deposition technique forcreating void free fill in very narrow dimension features.

SUMMARY

Methods of this invention relate to filling gaps on substrates with asolid dielectric material by forming a flowable film in the gap. Theflowable film provides consistent, void-free gap fill. The film is thenconverted to a solid dielectric material. In this manner gaps on thesubstrate are filled with the solid dielectric material. According tovarious embodiments, the methods involve reacting a dielectric precursorwith an oxidant to form the dielectric material. In certain embodiments,the dielectric precursor condenses and subsequently reacts with theoxidant to form dielectric material. In other embodiments, vapor phasereactants react to form a condensed flowable film.

One aspect of the invention relates to a method of depositing a soliddielectric material on a substrate having gaps, the method involving thesteps of (a) introducing a non-peroxide oxidant reactant and adielectric precursor reactant into a reaction chamber, such that thereactants are present in the chamber in vapor phase at the same time;(b) forming a flowable film at least in the gaps; and (c) reacting thesilicon-containing precursor and the oxidant to form a dielectricmaterial at least in the gaps. In certain embodiments the method furtherinvolves (d) converting the flowable film to the solid dielectricmaterial in the gaps. In certain embodiments, the converting the film in(d) occurs in the presence of the oxidant introduced in (a). In certainembodiments (a) through (d) are repeated at least once to build up afilm of a desired thickness.

In certain embodiments, the reactants react to form a condensed flowablefilm on the substrate. This film flows into the gap to fill the gap withthe dielectric material. The film is then converted to a soliddielectric material by one or more of various techniques including athermal anneal, ultraviolet (UV) exposure, microwave exposure, orexposure to an oxidizing plasma. According to certain embodiments, thefilm is converted to the solid material by mechanisms including (but notlimited to) cross-linking the precursor to produce the solid materialand/or removal of hydrogen (—H), hydroxyl (—OH) or water (H₂O) groups.In a particular embodiment, an inductively-coupled plasma is used toconvert the film.

According to various embodiments, the dielectric material is a siliconoxide, e.g., a doped silicon oxide containing boron and/or phosphorus.The precursor of the dielectric material may include one of more of thefollowing compounds triethoxysilane (TES), tetraethylorthosilane (TEOS),tetramethoxysilane (TMOS), methyl triethoxysilane (MTEOS),methyltrimethoxysilane (MTMOS), dimethyldimethoxysilane (DMDMOS),trimethylmethoxysilane (TMMOS), dimethyldiethoxysilane (DMDEOS),bis-triethoxysilylethane (BTEOSE) or bis-triethoxysilylmethane (BTEOSM),tetramethylcyclotetrasiloxane (TMCTS), octamethylcyclotetrasiloxane(OMCTS), and tetravinyltetramethylcyclotetrasiloxane (TVTMCTS). Incertain embodiments, the dielectric precursor is mixed in a carriersolvent, e.g., an alcohol.

According to various embodiments, the oxidant may be any suitableoxidant including water/steam, oxygen, ozone or peroxide. In particularembodiments, the oxidant in non-peroxide oxidant, e.g., water/steam,oxygen or ozone.

In certain embodiments, the forming the flowable film involvesselectively condensing the dielectric precursor in the gaps. Theprecursor may be selectively condensed due to the Kelvin effect. Theoxidant then reacts with the condensed precursor. In certainembodiments, the oxidant reactant is in the vapor phase when reacted. Incertain embodiments, reacting the liquid regions of the precursor withthe oxidant converts the film to a solid dielectric material.

Another aspect of the invention relates to a method of depositing asolid dielectric material on a substrate having gaps of dimension on theorder of about 100 nanometers or less. The method involves theoperations of (a) simultaneously introducing a silica-forming precursorand a second reactive material into a reaction chamber; (b) exposing thesubstrate to the precursor of the solid dielectric material, which is inthe vapor phase in order to achieve selective condensation in narrowgaps where the precursor is liquefied due to the Kelvin effect; and (c)reacting the precursor liquid regions with the second reactive materialto form a dielectric material in the gaps. The second reactive materialmay be an oxidant, e.g., water or steam.

These and other features and advantages of the invention will bedescribed in more detail below with reference to the associateddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a rough schematic cross-sectional diagram of a trenchpartially filled by a conventional method.

FIG. 2 is a process flow diagram depicting a method according to oneembodiment of the invention.

FIG. 3 is a process flow diagram depicting a method according to oneembodiment of the invention.

FIGS. 4 a-4 c are process flow diagrams, each depicting a methodaccording to an embodiment of the present invention.

FIGS. 5 a-5 e illustrate a series of cross sections of a substrate withgap features of size less than 100 nm. The cross sections follow anexemplary process of this invention.

FIG. 6 illustrates the relationship between percent liquid phase (of atwo phase component) and partial pressure of the component in small gap.The depicted hysteresis in the relationship results from the Kelvineffect.

FIG. 7 shows how the magnitude of the hysteresis effect (due the Kelvineffect) varies as a function of feature size (as illustrated by the gapwidth for linear trenches) for water at 100° C. and TEOS at 20° C.

FIGS. 8-10 are block diagram depicting some components of variousreactors suitable for performing certain embodiments of the invention.

FIG. 11 shows an embodiment of the reaction chamber utilizing a baffleplate assembly to increase precursor utilization.

FIG. 12 shows FTIR spectra of a dark-deposited film before and afterexposure to an oxygen plasma.

FIG. 13 is a microscope image showing circular growth of the flowablefilm caused by a completed reaction between the silicon and oxidantprecursors.

FIG. 14 is a microscope image showing irregular growth of the flowablefilm caused by incomplete reaction between silicon and oxidantprecursors due to the presence of an alcohol inhibitor.

DETAILED DESCRIPTION

The present invention relates to deposition processes that providecomplete gap of fill high aspect ratio (typically at least 3:1), narrowwidth gaps. Most deposition methods either deposit more material on theupper region than on the lower region of a sidewall or form cusps (alsocalled top-hats) at the entry of the gap. To remove sidewall and top-hatdeposits and keep the gap open for further deposition, conventional HDPCVD processes typically use a multi-cycle deposition process—etchprocess. Each cycle includes a deposition step followed by an etch stepTypically, fluorine species are used in the etch step. These fluorineetch steps are costly and time-consuming, in some cases requiringmultiple reactors.

FIG. 1 shows a rough schematic of a trench partially filled by aconventional HDP CVD method. Reference number 101 indicates wheresidewalls have formed from film that has been sputtered away from thebottom of the trench and redeposited on the sidewalls of the trench.These sidewalls have pinched off preventing further deposition. Achemical etch is required to re-open the trench before dielectric filmcan be deposited in it. Multiple deposition-etch-deposition cycles arenecessary to fill high aspect ratio trenches or other features.Reference number 103 indicates a weak spot. Conventional gap fillmethods often lead to the formation of weak spots in the dielectricfilm. Weak spots may form as a result of the increased gap volume to gapaccess area as the gap closes off, and can lead to voids or seams in thegap and ultimately device failure. Other known methods of gap-fill alsorely on multi-cycle deposition methods and are susceptible to pinch-offat the top of the gap, and void and seam formation in the gap.

The present invention provides gap-fill methods that result in good,seamless and void-free gap fill. The methods involve depositing a softjelly-like liquid or flowable film in the gap and then converting theflowable film into a solid dielectric film. The methods of the presentinvention reduce or eliminate the need for etch steps. In certainembodiments, a single cycle may be performed to fill a gap. In otherembodiments, a multi-cycle process may be used to fill a gap.

Certain embodiments of the invention involve reacting a dielectric(e.g., a silicon-containing) precursor with an oxidant. The reactantsare typically in the vapor phase and react to form a condensed flowablefilm. FIG. 2 is a process flow sheet depicting a method an example ofthis embodiment. As shown, a deposition process 200 begins at operation201 in which a substrate containing a gap is provided to a reactionchamber. Providing the substrate to the reactor may involve clamping thesubstrate to a pedestal or other support in the chamber. For thispurpose, an electrostatic or mechanical chuck may be employed.

After the substrate is provided to the reaction chamber, a process gasis introduced at operation 203. The process gas includes asilicon-containing compound and an oxidant. The gas may also include oneor more dopant precursors. Sometimes, though not necessarily, an inertcarrier gas is present. In certain embodiments, the gases are introducedusing a liquid injection system. Typically the silicon-containingcompound and the oxidant are introduced via separate inlets. In certainembodiments the oxidant is doped with a compound that contributes toreducing the reaction rate at the wafer surface. Examples of dopantcompounds that reduce the reaction rate include alcohols, e.g., ethanoland isopropyl alcohol. Reducing the reaction rate at the wafer surfacemay be desirable to facilitate continuous film propagation and growth.Also, in certain embodiments, the reactants may be provided in mannerthat increases residence time over the wafer surface. For example, insome embodiments, an inert gas (e.g., He, Ar or N₂) ballast is providedto increase reactant utilization. The ballast is provided below a baffleplate assembly. This constricts the flow of reactants thereby increasingtheir resident time over the wafer substrate. Dopant compounds such asboron or phosphorous-containing compounds may also be used to depositdoped oxide dielectric films.

The substrate is then exposed to the process gas at operation 205.Conditions in the reactor are such that the silicon-containing compoundand the oxidant react and condense. As shown in operation 207, aflowable film is thereby deposited on the substrate surface. Thesubstrate is exposed to the process gas for a period sufficient todeposit a flowable film to fill the gap. The deposition processtypically forms soft jelly-like film with good flow characteristics,providing consistent fill. The deposited film may also be describedherein for the purposes of discussion as a gel having liquid flowcharacteristics, a liquid film or a flowable film.

Process conditions in the reactor are such that the reaction product isa condensed material that is deposited on the surface. In manyembodiments, this involves bringing the substrate into the chamber under“dark”, i.e., non-plasma conditions. The substrate is not exposed to aplasma during the deposition phase (steps 205 and 207) of the process.Although not indicated on the flow sheet, gaseous byproducts may becontinuously pumped from the reaction chamber.

After the flowable film has been deposited in the gap, the as-depositedflowable film is converted to a silicon oxide dielectric film inoperation 209. In some embodiments, the film is converted by exposure toa plasma containing, for example, one or more of oxygen, helium, argonand water.

The process gas contains a silicon-containing compound and an oxidant.Suitable silicon-containing compounds include organo-silanes andorgano-siloxanes. In certain embodiments, the silicon-containingcompound is a commonly available liquid phase silicon source. In someembodiments, a silicon-containing compound having one or more mono, di,or tri-ethoxy, methoxy or butoxy functional groups is used. Examplesinclude, but are not limited to, TOMCAT, OMCAT, TEOS, tri-ethoxy silane(TES), TMS, MTEOS, TMOS, MTMOS, DMDMOS Diethoxy silane(DES),triphenylethoxysilane, 1-(triethoxysilyl)-2-(diethoxymethylsilyl)ethane,tri-t-butoxylsilanol and tetramethoxy silane. Examples of suitableoxidants include ozone, oxygen, hydrogen peroxide and water.

In some embodiments, the silicon-containing compound and the oxidant aredelivered to the reaction chamber via liquid injection system thatvaporizes the liquid for introduction to the chamber. The reactants aretypically delivered separately to the chamber. Typical flow rates of theliquid introduced into a liquid injection system range from 0.1-5.0mL/min per reactant. Of course, one of skill in the art will understandthat optimal flow rates depend on the particular reactants, desireddeposition rate, reaction rate and other process conditions.

Acceptable silicon-containing compound/oxidant flow ratios are veryvariable, as there is typically only a single reaction. Examples ofsuitable ratios include 3:1-1:100.

The flowable film deposited on the substrate typically contains somecombination of Si—O, Si—H and Si—OH bonds. As discussed above, in manyembodiments, the reaction of the silicon-containing compound and theoxidant takes place in non-plasma conditions. The absence of RF power(or other plasma source) prevents the incorporation of organic groups inthe film. For example, in reaction between TES and steam, the chemicalreaction causes formation of a flowable film containing Si—OH, Si—H andSi—O bonds, while the ethoxy group is removed as a gaseous ethanolbyproduct. As discussed above with respect to FIG. 1, the byproduct iscontinuously pumped out.

As indicated above, in certain embodiments a chemical reagent that actsas an inhibitor to slow down the reaction between the silicon andoxidant precursors is used. Examples of such reagents include alcoholssuch as ethanol, isopropyl alcohol, etc. Ethanol is a by-product of theoriginal chemical reaction as shown in the equation below between thesilicon-containing precursor H—Si—(O—C₂H₅)₃ and the oxidant H₂O:

H—Si—(O—C₂H₅)₃+3H₂O→H—Si—(OH)₃+3C₂H₅OH

While not being bound by any particular theory, it is believed that theproviding ethanol along with the oxidant precursor causes the reactionto be slowed down due to only two of the ethoxy groups on thesilicon-containing precursor being converted. It is believed that theremaining ethoxy groups serves to network the film by acting as a link.Depicted below is one embodiment of this method using a 25-90% molarsolution of ethanol:

Film composition depends in part on the oxidant chosen, with a weakeroxidant (e.g., water) resulting in more Si—H bonds than a strongeroxidant (e.g., ozone). Using ozone will result in conversion of most ofthe Si—H bonds to Si—OH bonds. An exemplary reaction according to oneembodiment of the invention between an organo-silane precursor(R_(4-x)—SiH_(x)) and peroxide (H₂O₂) produces a silanol gel(R—Si(OH)_(x) as well as other byproducts that may be pumped out.

Reactions conditions are such that the silicon-containing compound andoxidant, undergo a condensation reaction, condensing on the substratesurface to form a flowable film.

As discussed above, the reaction typically takes place in dark ornon-plasma conditions. Chamber pressure may be between about 1-100 Torr,in certain embodiments, it is between 5 and 20 Torr, or 10 and 20 Torr.In a particular embodiment, chamber pressure is about 10 Torr.

Substrate temperature is typically between about −20 and 100 C. Incertain embodiments, temperature is between about 0 and 35 C. Pressureand temperature may be varied to adjust deposition time; high pressureand low temperature are generally favorable for quick deposition. Hightemperature and low pressure will result in slower deposition time.Thus, increasing temperature may require increased pressure. In oneembodiment, the temperature is about 5 C and the pressure about 10 Torr.

Exposure time depends on reaction conditions as well as the desired filmthickness. Deposition rates are typically from about 100 angstroms/minto 1 micrometer/min.

Showerhead (or other gas inlet) to pedestal distance should also besmall to facilitate deposition. Showerhead-pedestal distance istypically ranges from about 300 mil-5 inches. In some embodiments, itranges from about 300 mil-1 inch.

A baffle plate assembly is utilized in certain embodiments to constrictreactant flow, thereby increasing the residence time of the silicon andoxidant precursors above the wafer substrate. The baffle plate assemblyis mechanically attached to the chamber body and tends to be at the sametemperature of the chamber walls (i.e., >30 C) to prevent depositionfrom occurring on the baffle plates. The change in conductance isachieved by providing an inert gas ballast below the baffle plates.Examples of inert gases that may be used include He, Ar and N₂. Typicalflow rates for the ballast vary from 100 sccm to 5 slm for the inertgases. In one embodiment a flow of 2 slm of He is used to create aballast. A schematic of a deposition using baffle is depicted in FIG. 11and discussed further below.

After the flowable film is deposited on the substrate, it is convertedto a solid silicon dioxide film. In certain embodiments, this conversionmay involve removal of hydrogen (—H), hydroxyl (—OH) or water (H₂O)groups to produce the solid material. The removal of hydrogen (—H),hydroxyl (—OH) or water (H₂O) groups may occur by thermal anneal,ultraviolet (UV) exposure, microwave exposure, or exposure to anoxidizing plasma.

According to various embodiments, the film may be converted to a solidoxide film by exposure to a plasma. This results in a top-downconversion of the flowable film to a solid film. Oxygen, helium, argonand steam plasmas are examples of plasmas that may be used. The plasmamay also contain one or more of these compounds. Nitrogen-containingplasmas should be avoided if the incorporation of nitrogen in theresulting dielectric film is undesirable. Temperatures during plasmaexposure are typically about 200 C or higher.

In certain embodiments, an oxygen or oxidizing plasma is used tofacilitate conversion of the Si—H bonds into Si—O bonds. Anoxygen-containing plasma may be particularly useful for flowable filmsthat have a high number of Si—H bonds, e.g., for films formed by thereaction of TEOS and steam.

Pressure is typically low, e.g., less than about 6 Torr. In certainembodiments, ultra-low pressures, on the order of about 0-10 mTorr areused during the conversion step. Using low pressure allows top-downconversion of the flowable film without leaving voids in the film.Without being bound by a particular theory, it is believed that lowpressure causes sites left vacant by the removal of —H and —OH groups tobe filled only by available oxygen radicals in the plasma.

Also in certain embodiments, inductively coupled (high density) plasmasare used to facilitate conversion. Si—OH sites may be converted to Si—Osites by thermal excitation. Use of an inductively coupled plasmaprovides a thermal environment that facilitates conversion of the Si—OHsites to Si—O sites as well as the oxygen ions and radicals that areable to react with the Si—H sites to convert them to Si—OH sites (whichmay then converted to Si—O sites by elevated temperature or otherexcitation).

The plasma source may be any known plasma source, including RF andmicrowave sources. In a RF plasma, plasma power is typically at leastabout 3000 W. Also the plasma-assisted conversion is preferablyperformed with a high frequency substrate bias.

In some embodiments, a thermal anneal may be used instead of or inaddition to a plasma to convert the film into a solid oxide. Thermalannealing may be performed in any suitable ambient, such as a water,oxygen or nitrogen ambient. Temperatures are typically at least about250 C, i.e. high enough to break the Si—OH bond. For example, thermallyannealing a silanol gel R—Si(OH)_(x) results in a silicon dioxide SiO₂film and water vapor. In some embodiments, microwave or UV curing mayalso be used.

Also in some embodiments, an oxidizing environment to convert Si—H sitesto Si—OH sites may be obtained by utilizing thermal, UV, microwave orplasma curing in the presence of one or more oxidants such as oxygen,ozone, steam, etc. In certain embodiments, providing an oxidizingenvironment in operation 209 may involve using the same oxidant flow asin operation 203.

An example of a process according to another embodiment is shown in FIG.3. In this embodiment, the flowable film is formed by first depositingthe silicon-containing precursor and then flowing steam to convert thefilm to the flowable liquid. As shown, the deposition process 300 beginsat operation 301 in which a substrate containing a gap is provided to areaction chamber. At operation 303, a process gas containing asilicon-containing precursor is introduced to the reactor. In thismethod, the process gas introduced in operation 303 does not contain anoxidant. Examples of silicon-containing precursors include TES and TEOS.A diluent gas such as helium or other suitable diluent may be used. Thenin operation 305, a solid silicon-containing layer is deposited on thesubstrate. Low RF power (less than about 400 W) is typically used todeposit the film. Substrate temperature is also typically fairly lowduring this step, for example, less than about 100 C. In someembodiments, the temperature may be less than about 20 C. In aparticular embodiment, the substrate temperature is subzero.

After the silicon-containing layer is deposited, a process gascontaining an oxidant is introduced to the reaction chamber in operation307. In specific example, the oxidant is H₂O (steam). The process gasmay be introduced with or without RF power. Substrate temperature istypically the same as for operation 305. The water or other oxidantoxidizes the solid film and converts it to a flowable film such as thatdescribed above with respect to operation 207 of FIG. 2 in operation309. The oxidizer in one embodiment is water with a flow rate varyingfrom 0.1 to 5 ml/min flow rate. One of skill in the art will understandthat optimal flow rates depend on the degree of oxidation achieved andfilm conversion based on the kind of silicon precursor utilized Theflowable film is then converted to a solid silicon oxide film inoperation 311. A plasma or thermal anneal, as discussed above, may beused in operation 311.

In other embodiments of the invention, a dielectric precursor isselectively condensed in a gap. According to various embodiments, athermodynamic effect due to which liquid remains selectively condensedin very narrow features is exploited. Under the certain physicalconditions the precursor liquid is either selectively deposited only inthe narrow features or the “bulk” precursor liquid is removed byevaporation while the liquid in the narrow features remains condensed.There, it is physically and/or chemically transformed to produce a soliddeposition material (e.g., dielectric). By selectively depositingmaterial in the narrow confined spaces of an integrated circuit, theprocess promotes “bottom up” filling. This results in the elimination ofvoids in the gap filling deposited material. The process has anadditional advantage deriving from selective deposition in trenches andother gaps. As a result, excess material is not formed on top of thefield regions and non-gap features of the partially fabricatedintegrated circuit. By reducing the quantity of such material, theinvention reduces the need for expensive and time-consuming materialremoval process such as chemical mechanical polishing (CMP).

In a typical embodiment, the liquid phase deposition precursor isinitially provided in a vapor phase at a partial pressure below itssaturation pressure. Then, its partial pressure is gradually increaseduntil it approaches the saturation pressure, at which point the materialbegins to condense as a liquid—first in the narrow trenches and othersmall features of the substrate. At the saturation pressure the liquidwill begin to condense in the field. In one approach, the pressurizationstep is stopped just below the saturation pressure after the liquid hascondensed in the features but before it condenses in the field. In asecond approach, the partial pressure is increased to a point somewhereabove the saturation pressure of the precursor. This relatively highpartial pressure is maintained until at least all of the narrow gaps arecompletely filled with the liquid condensate. Typically, additionalcondensate (referred to herein as “bulk liquid”) forms over theremainder of the substrate surface as well. To remove this bulk liquidwhile retaining the entrained liquid in the narrow features, the partialpressure of the precursor is now reduced to a point below its saturationpressure. At this pressure, the bulk liquid evaporates, while the liquidremains entrenched in the narrow features. This preference for liquid toremain condensed in the small spaces at pressures below the saturationpressure is due to the “Kelvin effect.”

The invention is not limited to vapor phase introduction of the liquidinto the narrow features. In other embodiments, the liquid may beintroduced by immersion, spray on and/or spin on techniques, forexample. In each of these instances, the liquid must be capable ofpenetrating into the narrow features where gap fill is desired.

At scales<100nm, the Kelvin effect is a significant contributor indetermining phase equilibria in trenches, pores and high aspect ratiostructures. If a liquid is in a confined space in contact with a surfacewhich it wets, the liquid interface will have a curvature and a pressuredifferential will exist across the interface such that the pressure inthe liquid is lower than the pressure in the vapor space above theinterface. This will prevent the liquid from evaporating even though theambient pressure is significantly lower than the saturation pressure.This implies that at conditions near saturation there would be selectivecondensation at the bottom of high aspect ratio structures due to theincreased curvature of the film. This invention takes advantage of thepropensity for liquids to condense preferentially and to remaincondensed in small features. This propensity is employed to selectivelyfill narrow features with liquid. The resulting liquid, localized insmall feature gaps is converted to the desired deposition material,typically a solid dielectric or metal. The invention makes use of theKelvin effect in several different process sequences to achieve gap-fillin high aspect ratio features. The relevant thermodynamics of thisprocess will be described in more detail below.

For context, one general process used to fill narrow-dimension gaps isillustrated in FIG. 4 a. In an initial operation 401, a substrate havingnarrow gaps (e.g., openings on the order of about 100 nm or less) isprovided. It is typically provided in a reaction chamber where theliquid precursor will be converted to a solid deposition layer. In somecases, however, the substrate may be initially provided in anenvironment that is not used for the actual deposition reaction. Formany applications, the substrate is a partially fabricated integratedcircuit or other electronic device. In such applications, the gaps maybe defined by (a) trenches and vias for, e.g., shallow trench isolation,damascene line structures in dielectric layers, or storage capacitors,(b) gate electrodes in active devices, (c) vias for tungsten or copperinterconnects, (d) metal lines after patterning, and the like.

In an operation 402, the substrate is exposed to a vapor phaseprecursor. Initially, the precursor may be provided at a partialpressure well below its saturation pressure. In this case, theprecursor's partial pressure is then increased to about its saturationpressure or higher. This is not required, however, as the precursor mayimmediately have a partial pressure at or near its saturation pressure.Regardless of how the desired partial pressure (about saturationpressure or higher) is reached, it is maintained there until theprecursor condenses in the narrow gaps. See operation 403. Typically,additional condensate (referred to herein as “bulk liquid”) forms on thesubstrate surface and larger dimension gaps as well. To remove this bulkliquid while retaining the entrained liquid in the narrow features,operation 404 reduces the precursor's partial pressure to a level belowits saturation pressure but above its “hysteresis pressure.” Hysteresispressure is the minimum partial pressure at which liquid remains in gapsof a defined size (under equilibrium conditions). The hysteresispressure is below the saturation pressure. Note that if the pressure isdriven too low (below the hysteresis pressure), even the liquid in thenarrow features will evaporate. The concept of a hysteresis pressurewill be explained further below. Thus, in an operation 405, theprecursor's partial pressure is maintained at the reduced level untilthe liquid precursor evaporates from the regions outside thenarrow-dimension gaps. While the partial pressure need not remain fixedduring operation 405, it should reside within a window between the lowerlimit (the hysteresis pressure) and the saturation pressure.Alternatively, the partial pressure of the liquid precursor may also bebrought below the saturation pressure by increasing the saturationpressure by heating the substrate or the chamber.

With the liquid precursor now selectively confined to narrow dimensiongaps, it may be appropriate to take advantage of this localization toselectively form structures in the gaps. Thus, in an operation 406, theliquid regions of the precursor are converted into a solid-phasedeposition material. This conversion may be achieved physically forexample simply by solidification or chemically by reacting the precursorliquid regions with another material to produce the solid material or bydecomposing or polymerizing the precursor using, for example, thermal orultraviolet means. Finally, in an optional operation 407, additionalsolid-phase material is deposited in regions outside of thenarrow-dimension gaps, including the larger dimension gaps that were notfilled by the above process. This additional deposition may beaccomplished using a conventional process such as CVD, physical vapordeposition (PVD), plasma assisted chemical vapor deposition (PECVD),high density plasma (HDP), spin on techniques, atomic layer deposition(ALD), pulsed nucleation layer (PNL) deposition, pulsed deposition layer(PDL), plating techniques (including electroplating and electrolessplating), etc. Alternatively, it may be accomplished by making use ofthe Kelvin effect as described above, but with different precursors orunder different partial pressures or with a different process sequence,etc. as appropriate for larger gap structures.

A second general process used to fill narrow-dimension gaps isillustrated in FIG. 4 b. Operations 401, 402, 406 and 407 are describedabove in reference to FIG. 4 a. Following 401 and 402 is operation 410,wherein the precursor's partial pressure is increased to a pressure justbelow its saturation pressure such that the precursor condenses in thenarrow gaps without bulk condensation. Steps 406 and 407 are thenperformed as described in reference to FIG. 4 a.

A third general process is illustrated in FIG. 4 c. In thisimplementation of the invention, steps 401, 404, 405, 406, and 407 areperformed in the same manner as in reference to FIG. 4 a. In place ofstep 402, step 412 is performed, wherein the substrate is exposed to aliquid precursor (e.g. by dip casting, spray on, print on, or spin onmethods). Step 403 is omitted.

To illustrate the selective condensation due to the Kelvin effect, onecan visualize what happens if a wafer with gap features less than 100 nmis brought in contact with a pure fluid (in vapor phase) at atemperature below its critical point and the fluid is pressurized to issaturation pressure and then depressurized as shown in FIGS. 5 a-5 e.These figures present cross-sections showing gaps typically encounteredin shallow trench isolation applications. As shown, a pad nitride 505(or other hard mask material) defines field regions 504 and trenches506. In this example the trenches 506 are formed in a silicon substrateand assumed to have a width of not more than about 100 nanometers. Thesidewalls of trenches 506 are lined with a nitride liner 508. Of course,other structures with gaps of similar dimensions will also exhibit theKelvin effect as depicted in FIGS. 5 a-5 e. Structures of differentshapes for examples vias or trenches or islands or structures withreentrant gaps will also exhibit the same qualitative behavior with somequantitative differences.

In FIG. 5 a, the material in question is present entirely as a vaporphase fluid at a partial pressure much lower than saturation pressure.At this pressure, some of the material is adsorbed onto the surface ofthe substrate to form a minimal adsorption layer 510, with no liquidphase yet in existence. When the partial pressure of the fluid is raisedto a point just below its saturation pressure, as shown in FIGS. 5 b and5 c, the fluid starts to condense in the smaller features and in thecorners of the larger features. This is due to the curvature of theadsorbent layer 510, which has characteristics of the liquid film. Notethat, as the fluid starts to condense, the narrower features are filledfirst. See condensed fluid in regions 512. As shown in FIG. 5 c, if thefluid's partial pressure is maintained in this range (at or nearsaturation pressure, but not significantly above saturation pressure),the vapor condenses in the narrow dimension trenches 506, but notelsewhere.

In FIG. 5 d, the partial pressure of the fluid has been raised to alevel above its saturation pressure, and fluid in the chamber condensesto a liquid state over the entire substrate. This includes largedimension gaps as well as field regions. The condensate in these regionsis referred to as bulk liquid. See condensate 514 in FIG. 5 d. Next, asshown in FIG. 5 e, the chamber is slowly depressurized and the bulkfluid 514 vaporizes while the condensate 512 remains entrained in thesmaller features. During the depressurization step, the curved interfaceis due to the condensed liquid in the features (rather than the absorbedfilm) and the curvature of this interface is much greater leading to amuch larger Kelvin effect. This causes a hysteresis loop inpressurization-depressurization cycle. Note that in the features in FIG.5, the neck dimension is larger than the rest of the feature. Thisprocess, however, is even more effective in instances where the neckdimension is smaller than or approximately equal to the rest of thefeature. Thus, the Kelvin effect (and the range of applicability of thisinvention) extends to reentrant features, features with facetedopenings, straight features, sloped features, etc. This process providesfor gap fill without voids, weak spots or seams as are often seen indirectional or conformal gap-fill processes. Also, gap-fill by thismethod does not encounter forbidden gaps as is common with ALD typetechniques where intermediate gap sizes are made inaccessible to bulkfill techniques.

FIG. 6 illustrates a generic hysteresis loop in acondensation-vaporization cycle due to the Kelvin effect insmall-dimension features. The vertical axis has units of percentage offluid in the liquid phase (100×mass of liquid/(mass of liquid+vapor)).The horizontal axis has units of partial pressure of the fluid.Initially, at very low pressure, the fluid is entirely in the gas phase(with some small quantity physically adsorbed on the surface). As thefluid's partial pressure approaches P_(sat)at a pressure P_(sat)−ΔP,condensate begins to form in the narrow dimension features and cornersof larger features. The arrows on the graph indicate the direction ofpartial pressure change. As partial pressure is increased, formation ofcondensate is increased. Eventually, as pressure is raised to P_(sat)and maintained at that pressure, 100% of the fluid will be in the liquidphase. In one embodiment of this invention where apressurization-depressurization cycle is used, the direction of pressurechange reverses so that fluid's partial pressure begins decreasing.Initially, some of the liquid begins vaporizing and the % liquid phasebegins decreasing. The liquid depressurization curve may for a timefollow the path of the pressurization curve as the bulk liquid andliquid in the large features evaporates. At some point, however, thesmall features will influence the process so that the Kelvin effectleads to an observed hysteresis, i.e., relatively more fluid will remainin the liquid phase for any given pressure (during depressurization). Ifthere were no small dimension features, no hysteresis would be observed.As the partial pressure continues to decrease, it will cross below thepressure at which fluid first began to condense during pressurization.However, on the return path (depressurization), a significant amount ofliquid remains entrained in the narrow dimension features and cornersdue to the presence of the curved vapor-liquid interface. Eventually, asthe fluid's partial pressure continues to drop, even the liquid in thenarrow features will evaporate. The point at which all fluid evaporatesfrom narrow features during depressurization is referred to herein asthe hysteresis pressure, P_(hyst).

In one method of practice of this invention where single or multiplepressurization-depressurization cycles are employed, it is important touse a final partial pressure within a window between a lower limit(referred to herein as the hysteresis pressure, P_(hyst)) and thesaturation pressure. By operating below the saturation pressure, most ifnot all of the bulk liquid should evaporate. By operating above thehysteresis pressure, at least some liquid will remain entrained in thenarrow dimension features. The above explanation suggests an embodimentof this invention: initially the substrate is provided with bulk liquidand liquid in narrow dimension features, and then the pressure isdecreased to a point between the hysteresis pressure and the saturationpressure and held there until the bulk liquid is removed and some liquidremains in the narrow dimension features. The initial wetting of thesubstrate may be accomplished in various ways including immersion,spraying, spin on techniques, etc. Of course, it may also beaccomplished by exposure to vapor phase fluid at a partial pressure wellabove the fluid's saturation pressure. It can remain in this state untilat least the narrow dimension features are filled with liquid.Typically, some amount of bulk liquid will also be formed.

The size of the hysteresis loop depends on the magnitude of the Kelvineffect and therefore on the feature size and shape as well as thesurface tension of the liquid and can be calculated as the change infree energy due to evaporation of a differential volume (ΔV) of liquidin the confined space which equals the change in surface area (ΔA) timesthe surface tension as:

$\begin{matrix}{{n\; \Delta \; G} = {{{- \left( {\Delta \; V} \right)}\rho_{cond}{RT}\; {\ln \left( \frac{f}{f_{sat}} \right)}} = {\left( {\Delta \; A} \right){\gamma cos}\; \theta}}} & \lbrack 1\rbrack\end{matrix}$

where, γ is the surface tension, θ is the contact angle, ρ_(cond) is thedensity of the condensed phase fluid, f and fsat are the fugacities atpressures P and P_(sat).

For a trench on a wafer (assumed to be a rectangular one-dimensionaltrench with width d), equation 1 reduces to:

$\begin{matrix}{\left( \frac{f}{f_{sat}} \right) = {\exp \left( {- \frac{2{\gamma cos}\; \theta}{\pi {\rho_{cond}}{RT}}} \right)}} & \lbrack 2\rbrack\end{matrix}$

Similar equations can be derived for different feature shapes. Forfluids at relatively low partial pressures, fugacity can be approximatedby pressure. The main variables in applications of this inventioninclude “d,” the trench width and f, the fugacity associated with thehysteresis pressure, the maximum pressure at which some fluid remainsentrained in trenches of width d during depressurization.

This phenomenon is exploited in this invention to allow for gap-fill insmall features and trenches, which are essentially, confined spaces. Asshould be obvious by now, for a feature size of 45 nm, the fluid mayexist as a liquid at pressures well below the saturation pressure. FIG.7 shows the “size” of the hysteresis loop as calculated by equation 2for water at 100° C. and TEOS at 20° C. in trenches as a function offeature size. On the vertical axis, percent hysteresis is calculated byusing equation 3:

$\begin{matrix}{{\% \mspace{14mu} {Hysteresis}} = \frac{P_{Sat} - P_{Hyst}}{P_{Sat}}} & \lbrack 3\rbrack\end{matrix}$

As the feature length scales shrink, this selective condensation effectbecomes stronger, and provides a wider process window. In other words,at smaller dimensions, d, there is a wider range of operational partialpressures for which liquid will remain selectively entrained in narrowdimension features. The horizontal axis, which corresponds to dimensiond, is the gap width associated with the technology node for ICfabrication. At the 180 nanometer gap width, the percent hysteresis isonly relatively small. Dropping to the 130 nanometer node and then the70 nanometer node and beyond gives wider and wider process ranges. FIG.4 plainly illustrates the increased importance of the Kelvin effect asfeature sizes become smaller. Thus, while the invention may be usedprofitably for substrates features having principal dimensions on theorder of 100 nanometers, it will find increasing benefit for substrateshaving features with even smaller principal dimensions, on the order of80 nanometers, 50 nanometers, and beyond.

In terms of features on a substrate surface, this process is generallyapplicable to any substrate having gaps that fall within the“mesoporous” domain. It generally includes gaps having a dimension ofabout 100 nm or less. The invention also finds particular usefulness inthe context of gaps having relatively high aspect ratios (e.g., at leastabout 6:1, and sometimes 10:1 or above) and in the context of featureshaving a neck dimension narrower than the remainder of the feature.Although, as indicated above, the invention may be employed withfeatures of essentially any shape, including features with straightand/or sloped sidewalls, features with faceted openings, reentrantfeatures, etc.

It is notable that many substrates have a wide range of gaps sizes andshapes to be filled. The present invention is useful to fill thenarrowest of these. In the larger features, the Kelvin effect is muchless significant, and the liquid phase precursor will evaporate when thepartial pressure of the precursor is reduced slightly below thesaturation pressure (i.e., the window defined by percent hysteresis istoo small to be useful). Thus, the larger gaps can be filled with asecond process such as conventional CVD, plasma enhanced chemical vapordeposition (PECVD), including high density plasma chemical vapordeposition (HDP CVD), physical vapor deposition (PVD), atomic layerdeposition (ALD), subatmospheric chemical vapor deposition (SACVD),electroplating, electroless plating, etc.

As noted above, various precursors may be used depending on the desireddeposition material. In general, the precursor should have a saturationpressure that is reasonable for the range of temperatures and pressuresavailable for the process under consideration. As indicated by equation2, its liquid phase density, surface tension, and contact angle shouldbe appropriate for providing a relatively large window of operation(P_(lat)−P_(hyst)).

If a silicon oxide dielectric material is needed, precursors such assilanes and siloxanes may be appropriate. Examples of suitablesilica-forming compounds include TES, TEOS, tetramethoxysilane (TMOS),an organic alkoxysilane such as methyl triethoxysilane (MTEOS),methyltrimethoxysilane (MTMOS), dimethyldimethoxysilane (DMDMOS),trimethylmethoxysilane (TMMOS), dimethyldiethoxysilane (DMDEOS), abridged siloxane such as bis-triethoxysilylethane (BTEOSE) orbis-triethoxysilylmethane (BTEOSM), a cyclic siloxane such astetramethylcyclotetrasiloxane (TMCTS), octamethylcyclotetrasiloxane(OMCTS), tetravinyltetramethylcyclotetrasiloxane (TVTMCTS) and mixturesof these precursors. Another class of dielectric precursors is thepolysilazanes including perhydropolysilazanes (SiH₂NH₂)_(n), where n isan integer. These precursors have been applied as gapfill precursorsusing a spin on technique as discussed in US Patent No. 6,479,405, whichis incorporated herein by reference for all purposes. In the currentinvention, similar polymeric precursors of appropriate molecular weightcan be applied for gapfill by condensing from the vapor phase or byfirst applying to the substrate in the liquid phase followed byevaporation of the bulk liquid by the depressurization techniquedescribed previously.

In a typical scenario, the precursor liquid may be reacted with anothermaterial to produce the desired solid material. For example, an acid orbase catalyzed TEOS condensation process can be achieved selectively insmall features by using a multi-step process in which the first reactantTEOS is first condensed inside the features by pressurizing TEOS vaporto pressures greater than P_(sat). The chamber is then depressurized toa pressure P_(sat)−ΔP that is within the hysteresis loop for the largesttarget feature size. The ambient fluid is a vapor while the features arefilled with liquid TEOS. Then the second reactant (water/steam, ozone orperoxide) and catalyst (acid, e.g. HCl or base e.g. NH3) is added insuch a manner that it preferentially partitions into the liquid phasewhere the reaction occurs to form a silicon dioxide.

The same reaction can be carried out in a single step process, whereboth reactants are introduced into the chamber simultaneously and thepressure is slowly increased to a pressure just below the saturationpressure such that condensation and subsequent reaction occurs only inthe target features. The precursor(s) may also be mixed in a carriersolvent. Multiple pressure or temperature cycles can also be used toenhance mass transfer of reactants or by-products.

Alternately, the precursor liquid may be converted into a solid materialvia decomposition of the precursor in the liquid regions. For example,thermal decomposition or ultraviolet processes may be used.

With the choice of suitable chemistry and processing conditions, thefilm can be deposited in an entirely bottom-up manner, with the highestgrowth rate in the smallest structures.

In certain embodiments, the precursor(s) may be the vapor or liquid formof the final solid gapfill material. The gap-fill may be accomplished atan elevated temperature such that the material filling the features is aliquid, which subsequently solidifies as the substrate is cooled.

In any gap fill application where a doped material is desired, thedopant may be introduced by various procedures. For example, if a dopantprecursor has appropriate phase equilibria properties, it may beintroduced simultaneously as a vapor mixture. The dopant may also beintroduced sequentially.

Apparatus

The methods of the present invention may be performed on a wide-range ofreaction chambers. The methods may be implemented on any chamberequipped for deposition of dielectric film, including HDP-CVD reactors,PECVD reactors, any chamber equipped for CVD reactions, and chambersused for PDL (pulsed deposition layers).

The methods of the present invention can be implemented in manydifferent types of apparatus. Generally, the apparatus will include oneor more chambers or “reactors” (sometimes including multiple stations)that house one or more wafers and are suitable for wafer processing. Asingle chamber may be employed for all operations of the invention orseparate chambers may be used. Each chamber may house one or more wafersfor processing. The one or more chambers maintain the wafer in a definedposition or positions (with or without motion within that position, e.g.rotation, vibration, or other agitation). The various stations may bewholly or partially isolated by virtue of gas curtains, walls, etc. Insuch cases, the substrate may be indexed between different stationsduring a multistage process.

In certain embodiments, the present invention may be implemented in aHDP CVD reactor. An example of a suitable reactor is the Speed™ reactor,available from Novellus Systems of San Jose, Calif. In certainembodiments, the present invention may be implemented in a PECVDreactor. Examples of suitable reactors are the Sequel™ reactor and theVector™ reactor, both available from Novellus Systems of San Jose,Calif. In certain embodiments, the present invention may be implementedin a CVD chamber equipped for metal and/or dielectric deposition. Anexample of a suitable reactor is the Altus™ reactor available fromNovellus Systems of San Jose, Calif. In certain embodiments, the presentinvention may be implemented in a chamber equipped for atomic layerdeposition (ALD), pulsed deposition layer (PDL), or pulsed nucleationlayer (PNL) reactions. An example of such a reactor is the Altus™ withPNL reactor available from Novellus Systems of San Jose, Calif.

FIG. 8 provides a simplified schematic depicting one preferredembodiment of the invention. As shown, a reactor 800 includes a processchamber 801, which encloses other components of the reactor. A substrate816 (e.g., a partially fabricated integrated circuit) is placed upon apedestal 814. The pedestal may have an active temperature control system(not shown) to heat or cool the wafer. A vacuum pump 812 is used toevacuate the air from process chamber 801 via vacuum line 810. Isolationvalves 820 are used to retain the vacuum after the pump is turned off.The chamber can be pressurized and de-pressurized using an accuratepressure control system (not shown). A precursor is provided in vessel802 and allowed to sublimate (if a solid) or evaporate (if a liquid)into a carrier gas feed line 818. Alternately, a gas phase precursor maybe supplied (not shown). The precursor flow rate may be controlled, forexample, by altering the temperature of a liquid (or solid), bycontrolling the flow rate or residence time of the carrier gas, or bycontrolling the flow rate of a diluent gas to the chamber. The relevantisolation valve 820 may be used to separate the precursor vapor from thereactor and the carrier gas until a desired time. When the valve is thenopened, a carrier gas forces the precursor vapor into the chamber. Thecarrier gas may be any inert gas, such as nitrogen or argon. A diluentgas may be supplied through carrier line 806. The diluent gas may be anyinert gas such as noble gas (e.g., helium or argon), nitrogen (dependingon the process), carbon dioxide (depending on the process), etc. Ifdesired, a second reactant gas is supplied through line 808.

As indicated above, in certain embodiments, deposition is followed by aconversion to solid film that involves a thermal, UV, microwave orplasma process. These deposition sand conversion operations areperformed in the same reaction chamber. In other embodiments, thedeposition may be performed in a first chamber and then transferred to asecond chamber for a thermal or plasma anneal. For example, reactorsthat are configured for plasma reactions may be used for both thedeposition and plasma anneal operations. Other reactors may be used fordeposition and thermal anneal operations.

FIG. 9 shows an example of a reactor that may be used in accordance withcertain embodiments of the invention. The reactor shown in FIG. 9 issuitable for both the dark deposition and conversion to a solid film,for example, by plasma anneal. As shown, a reactor 900 includes aprocess chamber 924, which encloses other components of the reactor andserves to contain the plasma generated by a capacitor type systemincluding a showerhead 914 working in conjunction with a grounded heaterblock 920. A low-frequency RF generator 902 and a high-frequency RFgenerator 904 are connected to showerhead 914. The power and frequencyare sufficient to generate a plasma from the process gas, for example400-700 W total energy. In the implementation of the present invention,the generators are not used during dark deposition of the flowable film.During the plasma anneal step, one or both generators may be used. Forexample, in a typical process, the high frequency RF component isgenerally between 2-60 MHz; in a preferred embodiment, the component is13.56 MHz.

Within the reactor, a wafer pedestal 918 supports a substrate 916. Thepedestal typically includes a chuck, a fork, or lift pins to hold andtransfer the substrate during and between the deposition and/or plasmatreatment reactions. The chuck may be an electrostatic chuck, amechanical chuck or various other types of chuck as are available foruse in the industry and/or research.

The process gases are introduced via inlet 912. Multiple source gaslines 910 are connected to manifold 908. The gases may be premixed ornot. The temperature of the mixing bowl/manifold lines should bemaintained at levels above the reaction temperature. Temperatures at orabove about 80 C at pressures at or less than about 20 Torr usuallysuffice. Appropriate valving and mass flow control mechanisms areemployed to ensure that the correct gases are delivered during thedeposition and plasma treatment phases of the process. In case thechemical precursor(s) is delivered in the liquid form, liquid flowcontrol mechanisms are employed. The liquid is then vaporized and mixedwith other process gases during its transportation in a manifold heatedabove its vaporization point before reaching the deposition chamber.

Process gases exit chamber 900 via an outlet 922. A vacuum pump 926(e.g., a one or two stage mechanical dry pump and/or a turbomolecularpump) typically draws process gases out and maintains a suitably lowpressure within the reactor by a close loop controlled flow restrictiondevice, such as a throttle valve or a pendulum valve.

It should be noted that the apparatus depicted in FIG. 9 is but oneexample of an apparatus that may be used to implement this invention.FIG. 10 provides a simple block diagram depicting various reactorcomponents arranged as may be arranged in a HDP-CVD reactor that may beused in accordance with the invention. As shown, a reactor 1001 includesa process chamber 1003 which encloses other components of the reactorand serves to contain the plasma. In one example, the process chamberwalls are made from aluminum, aluminum oxide, and/or other suitablematerial. The embodiment shown in FIG. 10 has two plasma sources: top RFcoil 1005 and side RF coil 1007. Top RF coil 1005 is a medium frequencyor MFRF coil and side RF coil 1007 is a low frequency or LFRF coil. Inthe embodiment shown in FIG. 10, MFRF frequency may be from 430-470 kHzand LFRF frequency from 340-370 kHz. However, the invention is notlimited to operation in reaction chambers with dual sources, nor RFplasma sources. Any suitable plasma source or sources may be used.

Within the reactor, a wafer pedestal 1009 supports a substrate 1011. Thepedestal typically includes a chuck (sometimes referred to as a clamp)to hold the substrate in place during the deposition reaction. The chuckmay be an electrostatic chuck, a mechanical chuck or various other typesof chuck as are available for use in the industry and/or research. Aheat transfer subsystem including a line 1013 for supplying heattransfer fluid controls the temperature of substrate 1011. The waferchuck and heat transfer fluid system can facilitate maintaining theappropriate wafer temperatures.

A high frequency RF of HFRF source 1015 serves to electrically biassubstrate 1011 and draw charged precursor species onto the substrate forthe deposition reaction. Electrical energy from source 1015 is coupledto substrate 1011 via an electrode or capacitive coupling, for example.Note that the bias applied to the substrate need not be an RF bias.Other frequencies and DC bias may be used as well.

The process gases are introduced via one or more inlets 1017. The gasesmay be premixed or not. Preferably, the process gas is introducedthrough a gas supply inlet mechanism including orifices. In someembodiments, at least some of the orifices orient the process gas alongan axis of injection intersecting an exposed surface of the substrate atan acute angle. Further, the gas or gas mixtures may be introduced froma primary gas ring 1021, which may or may not direct the gases towardthe substrate surface. Injectors may be connected to the primary gasring 1021 to direct at least some of the gases or gas mixtures into thechamber and toward substrate. Note that injectors, gas rings or othermechanisms for directing process gas toward the wafer are not criticalto this invention. The sonic front caused by a process gas entering thechamber will itself cause the gas to rapidly disperse in alldirections—including toward the substrate. Process gases exit chamber1003 via an outlet 1022. A vacuum pump (e.g., a turbomolecular pump)typically draws process gases out and maintains a suitably low pressurewithin the reactor.

In certain embodiments, high-cost features of the Speed™ or otherHDP-CVD tool may be eliminated. For example, the present invention maybe implemented on a HDP-CVD reactor without a dome and/orturbo-molecular pumps.

As indicated above, in certain embodiments, a CVD reactor may include abaffle assembly. FIG. 11 shows an embodiment of a CVD reactor thatincludes a baffle plate assembly. As shown in FIG. 11, oxidant andsilicon-containing precursor (as well as any dopant, carrier or otherprocess gases) enter the reactor 1101 through showerhead 1103 abovepedestal 1105, which supports the wafer. In the example depicted in FIG.11, H₂O and TES are the oxidant and silicon-containing precursor,respectively. The inert gas enters the chamber below baffle plates 1107at inlet 1109. In certain embodiments, the baffle plate is physicallyconnected to chamber body at the gas ring. A chamber manometer may alsobe located below the baffles. Use of the baffle plate and inert gasballast increases reactant residence time. In one example, a flow of2000 sccm He is used to provide the inert gas ballast. Baffle plates1107 may have holes that may be opened or closed.

Experimental

The following examples provide details illustrating aspects of thepresent invention. These examples are provided to exemplify and moreclearly illustrate these aspects of the invention and are in no wayintended to be limiting.

A flowable film was deposited in gaps on a substrate under darkconditions as described above with reference to FIG. 2. Substratetemperature was around room temperature for the deposition. Theprecursors used were TES (tri-ethoxy silane) and steam.

After deposition, the film was exposed to an oxygen plasma for 270seconds. Oxygen flow rate was 500 sccm and RF power was 9000 W. Thewafer substrate temperature during the plasma treatment was ˜500 C.

FIG. 12 shows FTIR spectra of the dark deposited flowable film and theplasma treated film. As can be seen from FIG. 12, Si—H, Si—OH and Si—Obonds are present in the dark deposited film. Treatment with an oxygenplasma results in removal of the —OH group, near elimination of the Si—Hbonds and a considerable increase in the main Si—O bond.

A similarly deposited film was exposed to helium plasma for 60 seconds.The helium plasma treatment was observed to remove the Si—OH bonds. Nochanges were observed in the Si—H bonds. A similarly deposited film wasexposed to a steam plasma for 180 seconds. The steam plasma treatmentwas observed to remove the Si—OH bonds and cause a slight decrease inSi—H bonds. A slight increase in Si—O bonds was also observed.

FIG. 13 shows a microscope image of a film deposited under conditionsthat allowed the silicon-containing precursor and oxidant reaction toreach completion. As can be seen, the image shows perfect circulargrowth spots 1301—indicating that the reaction has reached completion.

A film was deposited with isopropyl alcohol added to steam oxidant. FIG.14 shows a microscope image of the resulting film. As can be seen inFIG. 14, the microscope image shows irregular grain boundaries 1401,unlike the circular growth depicted in FIG. 13. Without being bound by aparticular theory, it is believed that the ethoxy group remains attachedto silicon and aids in networking the film by acting as a link. Thisindicates that the addition of an alcohol inhibitor to the oxidantprecursor aids in reducing the reaction rate. This reduction in reactionrate prevents the reaction from reaching completion, due to incompleteconversion of all ethoxy groups caused by an oxidant deficiency.

Other Embodiments

While this invention has been described in terms of certain embodiments,there are various alterations, modifications, permutations, andsubstitute equivalents, which fall within the scope of this invention.It should also be noted that there are many alternative ways ofimplementing the methods and apparatuses of the present invention.Further, there are numerous applications of the present invention, bothinside and outside the integrated circuit fabrication arena. It istherefore intended that the following appended claims be interpreted asincluding all such alterations, modifications, permutations, andsubstitute equivalents as fall within the true spirit and scope of thepresent invention.

What is claimed is:
 1. A method comprising: introducing vapor phasecompounds including a dielectric precursor reactant and a catalyst intoa reaction chamber; and forming a flowable film on a substrate in thereaction chamber by a catalyzed condensation reaction.
 2. The method ofclaim 1, wherein the dielectric precursor reactant is a silane or asiloxane.
 3. The method of claim 1, wherein the dielectric precursor istriethoxysilane (TES), tetraethylorthosilane (TEOS), tetramethoxysilane(TMOS), methyl triethoxysilane (MTEOS), methyltrimethoxysilane (MTMOS),dimethyldimethoxysilane (DMDMOS), trimethylmethoxysilane (TMMOS),dimethyldiethoxysilane (DMDEOS), bis-triethoxysilylethane (BTEOSE) orbis-triethoxysilylmethane (BTEOSM), tetramethylcyclotetrasiloxane(TMCTS), octamethylcyclotetrasiloxane (OMCTS),tetravinyltetramethylcyclotetrasiloxane (TVTMCTS) and mixtures thereof.4. The method of claim 1, wherein the dielectric precursor is a vaporphase polymeric precursor.
 5. The method of claim 1, wherein thecatalyst is a base.
 6. The method of claim 1, wherein the catalyst is anacid.
 7. The method of claim 1, wherein the process gases furthercomprise an alcohol.
 8. The method of claim 1, wherein the process gasesfurther comprise a solvent.
 9. The method of claim 1, wherein thesubstrate is not exposed to a plasma during formation of the flowablefilm on the substrate.
 10. The method of claim 1, wherein the flowablefilm at least partially fills a gap on the substrate.
 11. The method ofclaim 1, further comprising reacting the flowable film with a secondreactant.
 12. The method of claim 1, further comprising reacting thedielectric precursor with a second reactant to form the flowable film.13. The method of claim 1, wherein the oxidant reactant and dielectricprecursor reactant are introduced to the reaction chamber sequentially.14. The method of claim 1, further comprising exposing the flowable filmto species generated by a plasma source.
 15. The method of claim 1,further comprising exposing the flowable film to ultraviolet ormicrowave radiation.
 16. The method of claim 1, wherein the substratetemperature is between about −20° C. and 100° C. during formation of theflowable film.
 17. A method comprising: introducing process gasesincluding a dielectric precursor reactant, a second reactant, and acatalyst into a reaction chamber; and reacting the dielectric precursorreactant with the second reactant to form a flowable film on a substratein the reaction chamber.
 18. The method of claim 17, wherein forming theflowable film comprises contacting the substrate with the dielectricprecursor reactant in vapor phase to a partial pressure at or below thesaturation pressure of the dielectric precursor reactant.
 19. The methodof claim 17, wherein forming the flowable film comprises contacting thesubstrate with the dielectric precursor reactant in vapor phase at apartial pressure of at least about the saturation pressure of theprecursor reactant and further comprising subsequently reducing thepartial pressure of the dielectric precursor reactant to a level belowits saturation pressure.
 20. The method of claim 17, further comprisingexposing the flowable film to ultraviolet or microwave radiation. 21.The method of claim 17, further comprising exposing the flowable film tospecies generated by a plasma source.
 22. The method of claim 17,wherein the flowable film at least partially fills a gap on thesubstrate.